AQA GCSE Combined Science: Synergy — Paper 4 (Physical Sciences, Higher Tier)

Total marks: 100 · Duration: 105 minutes · Tier: higher

Instructions to candidates

Answer all questions in the spaces provided.
You are expected to use a calculator and a copy of the periodic table.
This paper assesses Topics 4.5–4.8 with greater emphasis on the required practicals and the analysis and evaluation of data.
The maximum mark for this paper is 100. The marks for each question are shown in brackets.

Paper

Section A — Multiple Choice (6 marks)

1. The relative charge on an electron is: (1 mark) A) +1 B) 0 C) −1 D) +2

2. Which is the test for hydrogen gas? (1 mark) A) Glowing splint relights B) Squeaky pop with a lighted splint C) Limewater turns cloudy D) Damp litmus bleached

3. A reaction that takes in energy, lowering the temperature, is: (1 mark) A) exothermic B) endothermic C) neutral D) reversible only

4. The rate of a reaction increases with temperature because particles: (1 mark) A) move slower B) collide more often and with more energy C) get larger D) stop reacting

5. A step-down transformer is used to: (1 mark) A) increase voltage B) decrease voltage C) change a.c. to d.c. D) increase current losses

6. Which method extracts copper from low-grade ores using bacteria? (1 mark) A) Phytomining B) Bioleaching C) Electrolysis only D) Fractional distillation

Section B — Structured Questions (60 marks)

7. A required practical measured the temperature change of a reaction. (4.7.3) (a) State whether a reaction that causes the temperature to rise is exothermic or endothermic. (1 mark) (b) Explain why a polystyrene cup is used in this practical. (2 marks) (c) Describe how you would investigate the temperature change when an acid is neutralised by an alkali. (3 marks)

8. Electrolysis breaks down compounds. (4.7.5) (a) Name the products at the cathode and anode when molten lead bromide is electrolysed. (2 marks) (b) Explain why a compound must be molten or dissolved for electrolysis to work. (2 marks) (c) State what is produced at the cathode during the electrolysis of copper sulfate solution, and explain why. (2 marks)

9. Acids react with bases and metals. (4.7.3) (a) Complete: acid + metal → salt + ______. (1 mark) (b) Describe how to make pure, dry copper sulfate crystals from copper oxide and sulfuric acid. (4 marks)

10. Rates of reaction can be measured (required practical). (4.7.4) (a) Describe the "disappearing cross" method for measuring rate. (3 marks) (b) Explain how increasing the concentration affects the rate using collision theory. (2 marks)

11. Forces and motion can be analysed with graphs. (4.7.1) (a) State what the gradient of a velocity–time graph represents. (1 mark) (b) State what the area under a velocity–time graph represents. (1 mark) (c) Calculate the kinetic energy of a 1000 kg car moving at 20 m/s. (2 marks)

12. Electromagnetic induction is used in transformers. (4.6.3) (a) Explain why transformers only work with alternating current. (2 marks) (b) A transformer has 200 primary turns and 50 secondary turns, with a 230 V primary supply. Calculate the secondary voltage. (3 marks)

13. Energy resources and efficiency. (4.8.2) (a) Give one advantage and one disadvantage of using wind power. (2 marks) (b) State what happens to "wasted" energy in a system. (1 mark) (c) Explain why transmitting electricity at high voltage reduces energy losses. (2 marks)

Section C — Extended Response

14. Compare the structure and bonding of an ionic compound and a metal, and explain how each conducts electricity. (6 marks)

Mark Scheme

Section A: 1. C; 2. B; 3. B; 4. B; 5. B; 6. B. (6)

7 (a) exothermic (1). (b) good insulator (1); reduces heat loss for an accurate temperature change (1). (c) measure a fixed volume of acid and its start temperature (1); add measured volumes of alkali, stir (1); record the highest temperature / temperature change (1). (6)

8 (a) cathode: lead (1); anode: bromine (1). (b) the ions must be free to move (1) to carry charge to the electrodes (1). (c) copper (1); because copper is less reactive than hydrogen (1). (6)

9 (a) hydrogen (1). (b) add excess copper oxide to warm acid (1); filter off excess (1); evaporate to crystallisation point (1); leave to crystallise and dry (1). (5)

10 (a) place a flask over a cross (1); add reactants and time how long until the cross disappears (1); shorter time = faster rate (1). (b) more particles per volume (1); more frequent successful collisions per second (1). (5)

11 (a) acceleration (1). (b) distance travelled (1). (c) Eₖ = ½ × 1000 × 20² = ½ × 1000 × 400 = 200 000 J (1 method, 1 answer). (4)

12 (a) a.c. produces a continually changing magnetic field (1); needed to induce a p.d. in the secondary coil (1). (b) Vp/Vs = Np/Ns → 230/Vs = 200/50 (1); Vs = 230 × (50/200) (1) = 57.5 V (1). (5)

13 (a) advantage: renewable / no CO₂ when running (1); disadvantage: unreliable (depends on wind) / visual impact (1). (b) it is dissipated to the surroundings, usually as thermal energy (1). (c) high voltage means lower current (1); so less energy is wasted as heat in the cables (1). (5)

14 — Levels (6): Indicative: ionic compound = giant lattice of oppositely charged ions held by strong electrostatic forces; conducts only when molten/dissolved (ions free to move). Metal = giant lattice of positive ions in a sea of delocalised electrons; conducts in the solid state because the delocalised electrons are free to move and carry charge.

L3 (5–6): Both structures described and conductivity correctly explained for each.

L2 (3–4): Some structure/conductivity detail.

L1 (1–2): Simple statements.

Sample Answers with Examiner Commentary

Question 14 — Sample Answers

Grade 9 answer "An ionic compound is a giant lattice of positive and negative ions held together by strong electrostatic forces acting in all directions. It only conducts electricity when molten or dissolved, because then the ions are free to move and carry charge; when solid the ions are fixed in place. A metal is a giant lattice of positive metal ions surrounded by a 'sea' of delocalised electrons. It conducts electricity even when solid because these delocalised electrons are free to move through the structure and carry the charge." Mark: 6/6. Examiner commentary: Both structures are described accurately and the conductivity of each is explained with the correct reason (free-moving ions vs delocalised electrons), including why ionic solids do not conduct. Top band.

Grade 6 answer "Ionic compounds are made of ions and only conduct when melted or dissolved because the ions can move. Metals have delocalised electrons that move and carry charge so they conduct." Mark: 4/6. Examiner commentary: Correct on both conductivity explanations, but the structures (giant ionic lattice; metal ions in a sea of electrons) are not described, and it does not say why ionic solids fail to conduct. Adding those reaches the top band.

Question 12(b) — Sample Answers

Grade 9 answer "Vp/Vs = Np/Ns, so 230/Vs = 200/50. Rearranging gives Vs = 230 × (50/200) = 230 × 0.25 = 57.5 V." Mark: 3/3. Examiner commentary: Correct equation, substitution and answer — recognised as a step-down transformer.